Log Injection in Echo Go

Log injection in Echo Go occurs when user-controlled input is written directly to log files without proper sanitization, creating opportunities for log forging, injection of malicious content, and bypassing security monitoring. In Echo Go applications, this vulnerability typically manifests through Echo's structured logging system and HTTP context handling.

The most common Echo Go log injection vectors appear in middleware and request handlers. Consider this vulnerable pattern:

func vulnerableHandler(c echo.Context) error {
    userID := c.QueryParam("user_id")
    log.Printf("User %s accessed resource", userID) // Vulnerable to injection
    return c.String(http.StatusOK, "OK")
}

An attacker can inject newline characters and additional log entries by requesting: /endpoint?user_id=123%0AERROR%20Something%20bad%20happened. This creates forged log entries that appear legitimate, making incident investigation impossible.

Echo Go's middleware chain amplifies this risk. Custom middleware often logs request details without validation:

func loggingMiddleware(next echo.HandlerFunc) echo.HandlerFunc {
    return func(c echo.Context) error {
        log.Printf("[%s] %s %s %s", 
            c.Request().RemoteAddr, 
            c.Request().Method, 
            c.Request().URL.Path, 
            c.QueryParams().Encode()) // Query params can contain malicious content
        return next(c)
    }
}

The QueryParams().Encode() method serializes all query parameters, including those with newline characters or control sequences. An attacker can craft requests that inject arbitrary log content, including fake error messages, stack traces, or security events.

Echo Go's structured logging with logrus or similar libraries doesn't automatically prevent injection. The structured fields can contain unescaped user input:

log.WithFields(logrus.Fields{
    "user_id": c.QueryParam("user_id"), // Unsanitized input
    "action": "login_attempt",
}).Info("User action logged")

Structured logging formats like JSON can be corrupted when user input contains quotes or control characters, breaking log parsers and creating injection opportunities.

Detecting log injection in Echo Go applications requires both static code analysis and runtime monitoring. Static analysis should focus on Echo's context handling patterns where user input flows to logging functions.

middleBrick's API security scanner specifically detects log injection vulnerabilities in Echo Go applications through black-box testing. The scanner identifies endpoints that accept user input and analyzes whether that input appears in log outputs. For Echo Go applications, middleBrick tests:

• Query parameter injection into log messages
• Header injection through request metadata logging
• Body content injection in request logging middleware
• Structured logging field injection
• Log rotation and file injection scenarios

middleBrick's scanning methodology includes sending payloads with newline characters, control sequences, and log forging patterns, then analyzing the application's response and any exposed log interfaces. The scanner checks for Echo Go's default logging behavior and common middleware patterns.

Runtime detection in Echo Go can be implemented using custom middleware that validates log content before writing:

func logInjectionPreventionMiddleware(next echo.HandlerFunc) echo.HandlerFunc {
    return func(c echo.Context) error {
        // Sanitize inputs before logging
        safeParams := sanitizeQueryParams(c.QueryParams())
        log.Printf("[%s] %s %s %s", 
            c.Request().RemoteAddr, 
            c.Request().Method, 
            c.Request().URL.Path, 
            safeParams.Encode())
        return next(c)
    }
}

func sanitizeQueryParams(params url.Values) url.Values {
    sanitized := url.Values{}
    for key, values := range params {
        safeKey := sanitizeInput(key)
        safeValues := make([]string, len(values))
        for i, val := range values {
            safeValues[i] = sanitizeInput(val)
        }
        sanitized[safeKey] = safeValues
    }
    return sanitized
}

func sanitizeInput(input string) string {
    // Remove control characters and newlines
    return strings.Map(func(r rune) rune {
        if unicode.IsControl(r) {
            return -1
        }
        return r
    }, input)
}

This middleware prevents log injection by sanitizing all user inputs before they reach the logging system, blocking newline characters and control sequences that could create forged log entries.

Remediating log injection in Echo Go requires a defense-in-depth approach combining input sanitization, secure logging practices, and Echo-specific patterns. The primary defense is validating and sanitizing all user inputs before logging.

Echo Go's context handling provides several points for implementing secure logging. The most effective approach is creating a custom logger wrapper that automatically sanitizes inputs:

type SecureLogger struct {
    logger *log.Logger
}

func NewSecureLogger() *SecureLogger {
    return &SecureLogger{
        logger: log.New(os.Stdout, "", log.LstdFlags),
    }
}

func (sl *SecureLogger) Printf(format string, args ...interface{}) {
    sanitizedArgs := make([]interface{}, len(args))
    for i, arg := range args {
        sanitizedArgs[i] = sanitizeForLog(arg)
    }
    sl.logger.Printf(format, sanitizedArgs...)
}

func sanitizeForLog(input interface{}) interface{} {
    switch v := input.(type) {
    case string:
        return sanitizeInput(v)
    case []string:
        sanitized := make([]string, len(v))
        for i, s := range v {
            sanitized[i] = sanitizeInput(s)
        }
        return sanitized
    default:
        return input
    }
}

func sanitizeInput(input string) string {
    // Replace control characters with safe alternatives
    return strings.Map(func(r rune) rune {
        if unicode.IsControl(r) && r != '\t' && r != '\r' && r != '\n' {
            return '?'
        }
        return r
    }, input)
}

Integrate this secure logger into Echo Go applications by replacing direct log calls:

var secureLog = NewSecureLogger()

func secureHandler(c echo.Context) error {
    userID := c.QueryParam("user_id")
    secureLog.Printf("User %s accessed resource", userID) // Safe from injection
    return c.String(http.StatusOK, "OK")
}

For structured logging with Echo Go, use JSON marshaling with custom sanitization:

func logStructured(c echo.Context, action string, data map[string]interface{}) {
    safeData := make(map[string]interface{})
    for key, value := range data {
        safeKey := sanitizeInput(key)
        safeValue := sanitizeValue(value)
        safeData[safeKey] = safeValue
    }
    
    logEntry, _ := json.Marshal(safeData)
    log.Printf("[%s] %s %s", c.Request().Method, c.Request().URL.Path, string(logEntry))
}

func sanitizeValue(value interface{}) interface{} {
    switch v := value.(type) {
    case string:
        return sanitizeInput(v)
    case []string:
        sanitized := make([]string, len(v))
        for i, s := range v {
            sanitized[i] = sanitizeInput(s)
        }
        return sanitized
    default:
        return value
    }
}

Echo Go's middleware system enables centralized log injection prevention. Create a logging middleware that wraps all handlers:

func secureLoggingMiddleware(next echo.HandlerFunc) echo.HandlerFunc {
    return func(c echo.Context) error {
        // Log request with sanitized parameters
        params := c.QueryParams()
        safeParams := sanitizeQueryParams(params)
        
        secureLog.Printf("[%s] %s %s params:%v", 
            c.Request().RemoteAddr, 
            c.Request().Method, 
            c.Request().URL.Path, 
            safeParams)
            
        err := next(c)
        
        // Log response with status code
        if err != nil {
            secureLog.Printf("Handler error: %v", err)
        }
        
        return err
    }
}

This approach ensures all Echo Go applications using this middleware are protected against log injection attacks, regardless of individual handler implementations.